1. Field of the Invention
The invention relates to the field of paint spray booths and, in particular, to a filter monitoring system for the spray booth that insures that the maximum available filter life is obtained.
2. Description of Related Art
Environmental regulatory agencies requires self-disclosure of violations to the appropriate Government Agency. Heavy fines are applied to companies that fail to meet the clean air standards. Under this law, paint spray booths equipped with filter systems are closely monitored to prevent over spray from reaching the atmosphere. In addition, the operator within the booth must be protected. Thus spray booth monitoring systems are available that provide alarm signals when the filter(s) is near the end of its useful life.
For example, in U.S. Pat. No. 5,356,334 “Apparatus And Method For Airborne Particulate Booth” by R. D. Gray uses sensors to monitor the pressure drop across filters. A signal is provided when the filters are near the end of their useful life. The apparatus is primarily designed for use in powder type spray operations. Therefore, it uses a filter pulsing system to periodically unclog the filter(s). When the pulse rate becomes almost constant, the alarm signal is activated. The system also provides for signaling when the end of filter life is approaching and shutting down the system should the filter become clogged to a point that it is ineffective. However, it is not desirable to completely shut down the spray booth. There may be a considerable amount of particulate matter still in the spray booth.
Another example can be found in U.S. Pat. No. 5,554,416 “Automated Air Filtration And Drying System For Waterborne Paint And Industrial Coatings” by F. G. Scheufler, et al. Pressure sensors upstream and downstream of the main filter are used to monitor pressure drop across the filter. As the pressure drop increases, signaling filter loading, a signal is sent to a blower to increase the flow rate to compensate therefore. A series of lights illuminate as the blower speed increases indicating filter condition. Thus adequate warning is provided to the operator to turn off the spray booth prior to complete filter failure. However, such a system depends upon the alertness of the operator to shut down the spray booth. Thus there is always a possibility that of operator error. In addition, the Scheufler, et al. system does not compensate for initial filter condition.
Another example can be found in Published Patent Application No.: US 2002/0062788 Al “Apparatus And Method For Configuring Spray Coating Application Systems” by D. M. Czech, et al. Here a system to remotely monitor the performance of a spray-coating booth via the Internet and the like, however, no specific mention of filter monitoring is made.
U.S. Pat. No. 6,168,646 “Flow Rate Control Of Temperature Controlled Fluids” by W. L. Craig, et al. discloses the use a filter assembly including a first roller of fresh filter material and a take up roller. The filter is disposed across the airflow path. As the exposed portion of the filter becomes clogged, the pressure drop there across causes the exposed portion of the filter to distort. This causes the exposed portion of the filter to make contact with a switch, which activates the rollers causing the take up roller to pull unexposed filter material off the first roller across the flow path and winding up the clogged portion on the take up roller. However, no warning device is provided for indicating that the last portion of the filter is clogged.
U.S. Pat. No. 6,040,777 “Device And Process For Indicating The Exhaustion Of A Fan Filter” by K. Ammann, et al. also discloses a device for determining filter life. However, the filter is designed to remove gases from the air. A gas detection device measures the level of the gas and if it rises to a predetermined level, indicating filter saturation, an alarm signal is provided.
Thus it is well-established practice to monitor filter performance in a paint spray booth and the like. However, none of the prior art discloses a system that takes into account the initial pressure drop across a new filter may very from filter to filter. For example consider a filter where the end of useful life occurs when the pressure drop increase across the filter is 3 PSI. If the initial pressure drop reading is 0.5 PSI, then a significant portion of the filter life is lost. Furthermore, none of the prior art devices constantly monitors the pressure drop across the filter, so that any unusual increases or decreases that indicate a problem in the spray booth can be investigated. None of the prior art devices address the problem of particulate matter that maybe still in the air after the spray booth has been shut down.
Thus, it is a primary object of the invention to provide a filter monitoring system for a spray painting booth.
It is another primary object of the invention to provide a filter monitoring system for a spray painting booth incorporating a system to indicated filter status.
It is a further object of the invention to provide a filter monitoring system for a spray-painting booth that provides automatic shut off of the operation of the spray gun at a predetermined percentage of the filter life.
It is a still further object of the invention to provide a filter monitoring system for a spray painting booth that takes into account the initial pressure drop across the filter prior to establishing the expected life of the filter.
It is another object of the invention to provide a filter monitoring system for a spray painting booth that provides a warning if there is a discrepancy between the reading at the end of one paint spraying shift and the beginning of another.